1. Field of the Invention
The present invention relates to a secondary battery charging system for charging electrical energy in the necessity of initiating a start-up of an internal combustion engine mounted in a vehicle as a driving source power.
2. Description of the Related Art
Recently, a growing number of auxiliary apparatus or devices mounted on a vehicle and of functions thereof has increased the amount of current power consumption or a dark current while the vehicle is in idle or stops. This introduces a possibility of discharging a battery installed in a vehicle. In general, a built-in battery of a vehicle self-discharges while an engine of the vehicle is stopped and the amount of the charged electrical power is decreased gradually. A vehicle which does not run for a long time causes a remarkable voltage loss of the battery.
This phenomenon further decreases the capacity of the secondary battery because the balance between the charging and discharging is affected by the increase or change of electrical load of the vehicle during driving.
In general, the vehicle equipped with an internal combustion engine as a driving power source can start the internal combustion engine by an electrical power supplied from a battery. If an excess of discharging occurs in the battery, it becomes difficult to start the internal combustion engine. In order to avoid this phenomenon, there is a method to increase the capacity of the battery. However, this conventional manner introduces the limitation caused by increasing a weight and volume of the battery.
For example, various conventional techniques (1) to (4) have been disclosed in order to solve the above conventional drawbacks.
(1) Japanese laid open publication No. 2004-168263 has disclosed a manner to detect an excess discharging of a battery in advance, and to halt the supply of electrical power to various devices in which a dark current flows.
(2) Japanese laid open publication No. 2002-209301 has disclosed a manner to charge an electrical power of one battery to the other battery in a vehicle equipped with a plurality of batteries.
(3) Japanese laid open publication No. H10-070843 has disclosed an additional switching device for electrically interrupting the electrical path between a battery and auxiliary devices during the long stop of a vehicle engine for transportation thereof.
(4) Japanese laid open publication No. S59-114108 has disclosed a vehicle equipped with a solar cell, the electrical power generated in the solar cell can drive an air conditioner for cleaning the air in a compartment of the vehicle during stopping and also disclosed a configuration to charge residual electrical power of the solar cell into a battery such as a secondary battery.
However, the conventional technique (1) described above has still a drawback to discharge the electrical power accumulated in the battery at the stopping of the electrical power to the various devices. The conventional technique (2) above also has a drawback to limit the use of the feature only for a hybrid type vehicle (HV) driven by both electrical power and internal combustion engine. The conventional technique (3) has still a drawback to operate the switch to interrupt the electrical path for transportation by manual and a drawback to eliminate information stored in a memory during transportation. The conventional technique (4) also has a drawback of a difficulty to charge the battery when the vehicle is in a garage without sunshine.
Although it is possible to adopt another technique using a fuel cell system that has recently been available in which an electrical power is generated during the stop of a vehicle and a battery is charge by the generated electrical power, it still involves a drawback in that it has to get and keep hydrogen as a fuel for the fuel cell system.